Electric timing device



Dec. 16, 1958 sp 2,864,231

ELECTRIC TIMING DEVICE Filed March 17, 1954 2 Sheets-Sheet 1 Inventor:1:522 Hans Spfln er" by,a?fiw-(.

His Att oYney Dec. 16, 1958 H, SPRINGER 2,864,231

ELECTRIC TIMING DEVICE Filed March 17, 1954 2 Sheets-Sheet 2 Inventor'-Hams Spvm 6 His Attorne United States Patent ELEcrnrc TlMh DEVICE HansSp in er, Ashlanrl, l dass, assignor to General Electric Company, acorporation of New York Application March 17, 1954, Serial No. 4l6,774

5 Claims. (Cl. 5@23} This invention relates to electric clocks andtiming devices and has particular application to electric clocks of thetype to be operated from a low voltage direct current source such as astorage battery or dry cell. Electric clocks of this general type havefound considerable application in automobiles, boats, aircraft and othermovable craft and vehicles and for such applicaticns are adapted to beoperated from a storage battery or similar power source.

In household and similar applications for electric clrcl's where aControlled frequency source of alternetting current power is avai able,a synchronous motor is often provided to drive the clock mechanism. Thespeed at which the clock mechanism is driven is, in such a case,controlled by the frequency of the alternating current source, so thatno separate speed reg lating means need normally be provided. Inautomobile applications, however, where normally only a low voltage (i.e., 6 or 12 volts) direct current source is available, some means mustbe provided for regulating the speed at which the clock mechanism isdriven. governor for an electric clock which has no available externalsynchronizing signal must be self-contained, the operation of such agovernor is usually based on some form of resonance involvingoscillatory, vibratory or some other form of cyclic motion. Thus theinstantaneous speed of a clock mechanism controlled by this type ofgovernor is not constant but rather follows a cyclic pattern along withthe governor. Only the average speed of the clock mechanism is limitedto a substantially constant value while the instantaneous speed rapidlyaccelerates and decelerates above and below the average value.

One example of a governor of the above-mentioned type is the well knownbalance wheel type of escapement quite commonly employed in springdriven clocks and watches. This type of governor limits the averagespeed of the clock mechanism by repeatedly interrupting the movement ofthe clock gear train and bringing it to a complete halt usually around 4or 5 times a second. Although other types of speed limiting governorsfalling Within this category may or may not completely interrupt themovement of the clock mechanism in accomplishing the speed limitingfunction, they all have the common characteristic of intermittentlydecelerating the speed of the clock or timer mechanism and then allowinga period of acceleration.

Governors of this type have been found to perform satisfactorily and cangenerally be produced at a relatively low cost so that they are widelyused in clocks and timing devices requiring self-contained governors.However, the employment of such a. governor poses certain problemsarising from the rapid accelerations and decelerations of the clockmechanism. It is apparent that in order to minimize the driving forcerequired to acc rate the clock mechanism at the required rate and tominimize the inertia loads transmitted during apid deceleration period,the inertia of the rotating Since a I .periods.

parts must be kept as low as possible within the stress limits requiredfor a satisfactory operating life.

This consideration also applies to the driving mechanism of the clock.For this reason, among others, direct current torque motors have notheretofore been generally employed to drive clocks controlled by theabovementioned intermittent deceleration type of speed limitinggovernor, since the addition of the relatively large inertia of themotor would not only require that a much greater torque be developed inorder to achieve the proper rate of acceleration but would also causesevere inertia loads to be transmitted to the delicate components of themechanism during the rapid deceleration Such severe operating conditionswould cause a considerable reduction in the operating life of thecomponents of the clock mechanism. The problem is even more aggravatedwhere the balance wheel type of escapement is employed as a governorsince, in such a case, the movement of the clock mechanism isperiodically fully interrupted so that the inertia loads are even moresevere.

On the other hand, the reliability, accuracy and low cost generallyobtainable with self-contained governors operating on a resonanceprinciple have led others to retain this form of speed limiting meansand to devise other forms of driving mechanisms. For instance, it hasbeen a common practice in clocks of this type to employ a low inertiaspring motor as a drive means with the spring being recharged atintervals by means of a solenoid which is automatically energized whenthe spring discharges beyond a certain point. In this and other forms ofdriving means heretofore commonly employed to drive clocks havinggovernors of this type, the drive is of the intermittently operabletype. That is, the ultimate source of mechanical drive power isalternately energized and de-energized through some form ofautomatically actuable switching arrangement, the application of acontinuous torque from such a source being heretofore consideredundesirable by reason of the problems arising out of the relatively.high inertia of the electrical components required to develop such atorque. The intermittently operable typev of drive is, on the otherhand, subject to various problems such as that of switch contactdeterioration by reason of the repeated switch actuations, a problemwhich is quite serious with relation to obtaining a satisfactoryoperating life.

In addition to the above considerations, it can be appreciated thatclocks and timing devices for automobiles and similar vehicles mustoperate under a wide variety of conditions and are exposed to sand anddust atmospheres and similar conditions. Consequently, where a directcurrent motor driven clock or timing device is used, it is desirable toprovide means for preventing sand and dust and other foreign particlesfrom clogging the commutator and permanently interrupting contactbetween the brushes and commutator. In this same connection, it shouldbe apparent that the motor must operate continuously over the entirelife span of the clock and that consequently there is a danger that suchextended operation may under certain conditions result in corrosion orpitting of the commutator or brush contact surfaces. Therefore it isalso desirable that means he provided for automatically wiping thecommutator and brush contact surfaces in the event that the electricalpower is interrupted.

.A further consideration, which will be discussed herein, arisesfrom'the well known tendency of the balance Wheel escapement type ofgovernor to lock at rest in certain positions under starting conditionswhen the full operating torque is suddenly applied and maintained.

Accordingly, it is an object of this invention to pro vide an improvedtiming device driven by a' direct current torque motor and controlled byan intermittent deceleration governor of the above-mentioned type, whichis not subject to the, disadvantages set forth above.

it is another object of this invertion to provide an im proved directcurrent electric clock controlled by a balance wheel type of escapernentmechanism and driven by a direct current torque motor, in which meansare provided for coupl'ng the drive motor in driving relationship to theclock mechanism so as to avoid the occurrence of the above-mentionedinertia loads upon the intermittent interruptions of the clock mechanismmotion by the escapement.

it is a further object of this invention to provide an proved electricclock driven by a direct current torque motor in which means areprovided for rapidly rotatingthe motor in the reverse direction upon aninterruption of electrical power so that the brush and commutatorcontact surfaces are rapidly wiped in the reverse direc tion to removeforeignparticles and clean the contact surfaces.

it is still a further object of this invention to provide means forremovably mounting the motor in driving relationship to the clockmechanism so that the motor can be readily detached for servicing orreplacement purposes.

It is still another object of this invention to provide an improvedelectric clock driven by a direct current motor and controlled by abalance wheel escapement, in which means are provided to prevent lockingof the escapement mechanism at starting.

Briefly stated, in accordance with one aspect of this invention, acontinuously operable motor means, including a small direct current,commutator type torque mete ispr-ov'ded to drive the clock mechanism.The motor means is coupled in driving relationship to the clock geartrain through a resilient coupling means such as a coil spring and thespeed of the clock mechanism is regulated by an intermittentdeceleration type of governor which, in the embodiment illustrated, is aconventional balance wheel escapement. The resilient coupling serves toinsulate the drive motor from the rapid accelerations and decelerationsof the clock gear train and serves to minimize shock and inertia loadswhich occur during the deceleration and interruption of the gear trainmotion. The motor and spring driving arrangement is freely movable inthe reverse direction so that the spring is allowed to discharge andrapidly rotate the motor in the reverse direct cn in the event of anelectrical power interruption so that the brush and commutator contactsurfaces are rapidly wiped in the reverse direction to remove foreignparticles and clean the contact surfaces.

This invention will be better understood and other objects andadvantages will be apparent from the following description taken inconnection with the accompanying draw'ngs, and its scope will be pointedout in the appended claims.

Referring to the drawinggFig. 1 is a perspective view of a low voltage,direct current clock embodying this invention; Fig. 2 is a crosssectional view of the clock shown in Pig. 1 illustrating the arrangementof the clock mechan sm and drive motor components; Fig. 3 is an explodedview illustrating in perspective the arrangmrnt of the clock mechanismcompcnents and the motcrdrive pinion together with the resilientcoupling means; while Fig. 4 illustrates in perspective the motor rotorand the drive pinion.

The clock shown in Fig. 1 ha particular application to automobiles andcomprises an outer casing 1 provided with mounting tabs 2 for mountingthe clock on the instrument panel. A sweep second hand isprovided inaddition to the usual indicating hands and a knob 3 is provided to allowmanual adjustment of the minute and hour hands. The regulatingmechanism, which controls the speed of the clock, is adjustable throughthe agency of a shaft 4, which is provided with a suitable slot so thatit can be rotated by means of a screwdriver or similar tool. Theposition of the speed regulating mechanism can be observed through aslot 5 provided in the face of the clock.

The clock mechanism, shown in cross section in Fig. 2 and in theperspective in the exploded view of Fig. 3, is driven by a suitabledirect current, commutator type torque motor through a resilientcoupling means-such as a spring 6. The illustrated drive motor, shown incross section at 7 in Fig. 2, is of the type which is shown and claimedin application of Edgar A. Phaneuf, John R. Enochs and myself, SerialNo. 416,746, filed March 17, 1954, entitled Electric Motor and Method ofManufacture Therefor, now Patent Number 2,818,518, and assigned to theassignee of the present invention. It will be understood that Fig. 2illustrates this type of motor as part of a preferred embod'ment of thisinvention and that other types of low voltage, direct current torquemotors may be employed without departing from the scope of thisinvention.

Referring to Figs. 2 and 4, the drive motor shown comprises an outercasing 8 which positions and supports an annular field magnet 9. Therotor coils ill! are Y connected and symmetrically mounted as shown inFig. 4 and are supported on a shaft ll; which is rotatably mounted atone end in a bearing portion 12 provided in the housing 8 and at theother end in a bearing portion formed in a tab 13 which extend from amotor mounting plate 14 as shown in Fig. 3. The motor is prov'ded with acommutator llla made up of three segments which are connectedrespectively to the outer ends of the rotor coils 1d. The commutator isengaged by a pair of wire brushes 1111 which are connectible to a directcurrent power source through a pair of terminals &9.

As shown in Figs. 2, 3 and 4, a pinion 15 is mounted to rotate with themotor shaft ill and engages a gear 16 mounted on a bushing member 17which is in turn rotatably mounted on second hand shaft 18. The drivemotor means is coupled in driving relationship to the clock mechanismthrough a resilient coupling means such as the spr'ng member 6 whichresiliently connects the gear 16 with a gear 19 aflixed to the shaft 18.Since the gear 16 is rotatable with respect to the shaft 18, the motoroutput torque is transmitted through the spring 6 to the gear 19 whichdirectly drives the second hand shaft 1%. V

The speed of the clock mechanism is regulated by a suitable governor ofthe intermittent deceleratirn type such as a balance wheel escapementmechanism shown at 24) in Fig. 3. The escapement 20 comprises the usualelements including an escape wheel 21, a pivotally mounted rocker arm51, an oscillatory balance wheel 52, and a hairspring 26. This type ofescapement operates in a well known manner with the rocker arm pivotingback and forth and interacting w'th the escape wheel 21 t0 alternatelyinterrupt the motion of the gear train and then allow a brief period ofacceleration. The average speed of the clock gear tra'n is thus limitedto a substantially constant value by means of intermittent accelerationsand decelerations. The escape Wheel 25. is driven by gear It) whichengages a pinion 22 attached to the escape wheel shaft.

The escapement is provided with rdjusting means which can be manuallyactuated from the face of the clock by rotating the shaft 4. A pinion 23is attached to the end of the shaft 4 and engages a rctat bly mountedgear segment 24. An adjusting member 25, shown in two secticns in Fig. 3for convenience of illustration only, extends from the gear segment 24and engages a hairspring 26 adjacent a fixed support 27. The member 25moves with the gear segment 24 to change the effective length of thehairspring and thus control the speed of the escapement. An indicatingmember 28, shown in Fig. 2, is attached to the gear segment and has aportion thereon visible through the slot 5 to indicate the setting ofthe regulating mechanism.

As pointed out above, the second hand is driven through the spring 6 andthe gear 19 attached to the shaft 18. A pinion 29 is affixed to theshaft 18 and drives a gear 30 which is attached to shaft 31 by means ofa bushing 32. A pinion 33 rotates with the shaft 31 and drives gear 34which is mounted on minute hand sleeve 35 but is free to rotate relativethereto. The minute hand sleeve 35 extends concentrically with thesecond hand shaft 13 and is rotatably mounted on a bushing 50 which isafiixed to a mounting plate 36 and extends through a second mountingplate 37. The second hand shaft 13 is supported independently of theminute hand sleeve 35 in the elongated bushing 50. The minute handsleeve 35 extends through the gear 34 and engages a spring member 38which is compressed into engagement with the face of the gear 34 uponassembly of a bushing 53 to the minute hand sleeve. The spring 38provides a frictional drive between the gear 34 and the minute handsleeve 35 in order to allow adjustment of the indicating hands ashereinafter described. Since the torque required to drive the indicatinghands is relatively quite small, the gear 34 drives the minute handshaft through the spring member 33 without the occurrence of anyslipping action.

A pinion 39 is attached to the portion of the sleeve 35 extendingthrough the plate 37. The speed is reduced to drive the hour hand sleeve40 by gears 41, 42 and 43.

The knob 3, shown in Fig. l, is attached to a set shaft 44 which can bepulled forward against a spring 45 to bring gear 46 into engagement withthe gear 41 thereby allowing both the hour and minute hand shafts to bemanually rotated to the desired setting. Since the torque required torotate the gear 34 in the reverse direction is relatively very high, thesleeve 35 will slip relative to the gear 34 through the agency of thespring member 38 thereby allowing the indicating hands to be setindependently of the clock and motor drive mechanism.

The mounting plate 37 is attached in spaced relationship to the motormounting plate 14 by means of the spacer members 47 which are afiixed tothe mounting plate 14 and which are provided with suitable means such asthe threaded portions shown so that they can be secured to the mountingplate 37. The mounting plate 36 is attached in spaced relationship tothe motor mounting plate 14- by means of similar spacer membersindicated at 48 in Fig. 3 but not shown in Fig. 2.

The spacer members 47 are provided with internally threaded portionswhich extend into the motor mounting plate 14. The motor is in turnprovided with suitable mounting lugs which can be aligned with theinternally threaded portions of the spacers 4-7 so that the motor can beattached to the motor mounting plate by means of screws 54 extendingthrough the mounting lugs of the motor and into the internally threadedportions in the ends of the spacers 47. Thus the motor is freelyremovable as a unit so that it can be replaced or repaired withoutdisturbing the rest of the assembly.

The details of the various components having been set forth above, theoverall operation of the clock embodying this invention will now bedescribed.

The clock motor means, comprising the direct current electric motor andthe torque transmitting members extending from the motor up to theresilient coupling means 6, drives the intermittently movable gear trainthrough the resilient coupling 6. The rapid accelerations anddecelerations of the gear train are followed by the spring 6 but not bythe motor drive means by reason of the relatively high inertia of themotor rotor. The spring 5.? unwinds slightly during the accelerationperiod, since the motor is rotating at a continuously lower speed matelyits initial position by the continued rotation of the motor during theperiod in which the motion of the gear train is interrupted by theescapement.

The motor can therefore rotate continuously while driving theintermittently movable gear train. It is thus unnecessary to provideadditional torque to accelerate the much heavier motor rotor along withthe intermittent movements of the escapement controlled gear train,since the spring 6 will discharge slightly a small amount to providethis rapid movement. In addition, the inertia of the spring 6 is quitelow and hence the spring can stop suddenly along with the gear trainwithout transmitting any substantial additional shock loading beyond therelatively low torque exerted. This invention therefore not onlyeliminates the necessity for accelerating the motor means along with thegear train but also prevents the occurrence of the shock loads whichwould otherwise occur if the movement of the motor were also interruptedby the escapement mechanism.

The drive motor is unrestrained from reverse rotation so that if itshould lose its driving force, the small amount of energy stored in thespring 6 would cause relatively rapid reverse rotation of the motorthrough at least a portion of a revolution. Thus if the electricalcircuit were interrupted by reason of foreign particles sticking to thecommutator or by corrosion or pitting on the commutator or brush contactsurfaces, the motor would automatically be rapidly rotated in thereverse direction to allow the brush to again contact the commutator tocause the motor to again drive forward. Thus the brushes are rapidlywiped back and forth across the commutator so that in most cases anyforeign particles will be dislodged and the contact surfaces cleaned bythe wiping action. The spring 6 therefore not only provides a resilientcoupling which permits the motor to rotate continuously under normalconditions but also provides for an automatic Wiping action between thebrushes and the commutator segments in the event of an interruption ofelectrical power.

The resilient coupling spring also provides an additional advantage whena balance wheel escapement Is employed as the governor. It is well knownthat when this type of escapement is at standstill, the pallet pins onthe rocker arm have a tendency in certain positions to lock with theserrations on the escape wheel when the operating torque is suddenlyapplied and maintained on the clock mechanism. The provision of thecoupling spring 6 overcomes this disadvantage. Under starting conditionsthe running torque is applied gradually by reason of the presence of theresilient coupling 6 and the inertia of the motor rotor causes it tocharge the spring 6 beyond the normal operating point so that the rotorwill oscillate back and forth a number of times at starting to agitatethe escapement mechanism into motion. Both the gradual application oftorque and the agitating motion of the rotor serve to prevent locking ofthe escapement mechanism at starting.

It will be apparent that the size and other characteristics of thespring 6 will be affected by the particular configuration employed andby the magnitude of the shaft output torque delivered by the drivemotor. By way of example, in an electric clock embodying this inventionand designed for use in automobiles and similar vehicles, it was foundthat a drive motor having a shaft output torque in the rangeof .002 to.007 lb.-in. would perform satisfactorily in combination with a couplingspring meeting the following specifications:

Material: Spring steel.

Wire diameter: .010.

Free length of coiled spring: 0.250".

Total length of wire in spring: 5.077.

Effective length of wire in spring: 5.027".

Number of turns: 10.

inside diameter of coil: 0.150".

Angular spring constant: 19 per .001 ib.-in. torque,

The most important of these specifications from a performance standpointis the angular spring constant, the remaining features being moreconcerned with cost, physical size and so forth, it has been establishedthat in general springs having angular spring constants in the generalvicinity of 4 to 30 per .001 lb.-in. torque may be employed inarrangements wherein the output torque of the drive motor falls withinthe above-mentioned range of .002 to .007 lb.-in.

It will be apparent, of course, that other forms of resilient couplingsmay be utilized to provide the angular resilience between the motor andthe clock mechanism. And it will be realized that the above ranges ofmotor torques and spring constants may of course be substantially varieddepending on the size and configuration of the other componentsemployed. The above figures, however, serve to set forth a workablerelationship between the parameters involved in a particular embodimentof this invention and may be used as a basis for establishing the propermagnitudes of parameters for other sizes and configurations.

Although the particular clock described herein and embodying thisinvention is controlled by means of a balance wheel type of escapement,it will be'undersood that this invention is also applicable to othertypes of clocks and timing devices in which the speed is controlled orlimited by governors which operate to intermittently decelerate thespeed of the clock or timer movement even though such governors may ormay not fully interrupt the motion of the parts in accomplishing theirfunction.

it will also be understood that the scope of this invention is notlimited in its other aspects to the particular embodiment described, andthat various changes, cornbinatio-ns, substitutions or modifications maybe employed in accordance with these teachings Without departing inspirit or in scope from this invention in its broader aspects.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. Timing means comprising a gear train, escapement means interactingwith said gear train to permit said gear train to be advanced inintermittent steps at a substantially constant average speed, a directcurrent continuously operable torque motor having a high inertia rotorfor driving said gear train, a split commutator fixed to said rotor forrotation therewith, a plurality of brushes engaging said commutator forsupplying electrical power to said commutator, and a low inertia springconnecting said rotor to said gear train for causing said rotor tooscillate back and forth a number of times at starting to agitate theescapement into motion.

2. Timing means comprising a gear train, escapemen means interactingwith said gear train to permit said gear train to be advanced inintermittent steps at a substantially constant average speed, a directcurrent torque motor having a high inertia rotor for driving said geartrain, a plurality of windings mounted on said rotor, a split commutatorfixed to said rotor for rotation therewith, said windings beingconnected to said commutator, a plurality of brushes engaging saidcommutator for supplying electrical power to said windings, a lowinertia spring connecting said rotor to said gear train for causing saidrotor to oscillate back and forth a number of times at starting toagitate the escapernent into motion, said rotor being unrestrained fromrotating in a reverse direction under the influence of said spring whenthe electrical power to the windings of said rotor is interrupted,whereby reverse rotation of the rotor and commutator Y 8 with respect tosaid brushes facilitates cleaning of said brushes.

3. In an electric clock, the combination of a unitary supportingstructure comprising a plurality of mounting plates disposed inspaced-apart parallel relationship to each other, a gear train supportedon said unitary supporting structure and including a plurality of shaftsrotatably mounted on said mounting plates, said shafts extendingsubstantially perpendicular to said mounting plates, time indicatingmeans connected to be driven by said gear train, escapement controlmeans mounted in said unitary supporting structure to interact with saidgear train and limit the average speed thereof to a substantiallyconstant value by periodically interrupting the movement of said geartrain, a direct current torque motor having a high inertia rotor fordriving said gear train, said motor being removably mounted on one ofsaid-mounting plates, said motor rotor extending substantiallyperpendicular to said mounting plate, gear means fixed to said rotorextending through said one of said mounting plates, said gear meansbeing in mesh with said gear train, a plurality of windings mounted onsaid rotor, a split commutator fixed to said rotor for rotationtherewith, a plurality of brushes engaging said commutator for supplyingelectrical power to said commutator, and a low inertia spring having itsaxis arranged substantially perpendicular to said mounting platesdisposed in said gear train for resiliently connecting said escapementto said high inertia motor rotor for causing said rotor to oscillateback and forth a number of times at starting to agitate the escapementinto motion.

4. An electric clock operable from a low voltage direct current sourcecomprising time indicating means, a gear train connected in drivingrelationship to said time indicating means, a mechanical escapementarranged to interrupt periodically movement of said gear train to limitthe average speed thereof to a substantially constant level, a directcurrent torque motor having a high inertia rotor for driving said geartrain, a plurality of windings mounted on said rotor, a split commutatorfixed to said rotor for rotation therewith, a plurality of brushesengaging said commutator for supplying electrical energy to saidcommutator from said low voltage direct current source, an output shaftextending from said rotor and having a drive pinion fixed to rotatetherewith, a rotatably supported gear member engaging said drive pinion,and a low inertia spring interconnecting said gear member and said geartrain for causing said rotor to oscillate back and forth a number oftimes at starting to agitate the escapement into motion, said couplingspring being light, flexible, readily responsive and having low externalfriction.

'5. Timing means comprising a gear train, escapement means interactingwith said gear train to permit said gear train to be advanced inintermittent steps at substantially constant average speed, a directcurrent torque motor having a high inertia rotor for driving said geartrain, the rotor of said motor being unrestrained from rotation in areverse direction, and an angularly resilient low-inertia springconnecting said rotor to said gear train for causing said rotor tooscillate back and forth a number of times at starting to agitate theescapement into motion.

Hookham July 23, 1901 Holtz Feb. 14, 1928

